Concentrate derived from a milk product enriched in naturally occurring sialyllactose and a process for preparation thereof

ABSTRACT

A concentrate derived from milk or a milk product comprising sialyllactose in amounts higher than the normal amounts found in the milk or milk product and a process for preparation of such a concentrate by ultrafiltration and diafiltration using a thin film polyamide based membrane. The concentrate is suited for use in nutritional products.

FIELD OF THE INVENTION

The present invention relates to a milk derived sialyllactoseconcentrate for the use in foods especially intended for infants,children or elderly persons as well as foods for medical or dieteticpurposes and other food applications. The invention also comprises aprocess for producing the sialyllactose concentrate.

BACKGROUND OF THE INVENTION

Communication between cells is central and ubiquitous in the human body.Key players in these processes are extracellular carbohydrate moietiesbound to specific substances, e.g. different membrane molecules,cytokines or pathogens. One important component of these carbohydratemoieties is sialic acid, a nine-carbon monosaccharide present in mosthuman and animal tissues. The concentration of sialic acid is high intissues with high rates of processing and interaction such as the brain.It is present in all human body fluids, of which its content isespecially high in milk. Sialic acid can be synthesised by the body.

Sialic acid has gained much scientific focus the last two decades, seeWang, B. and Brand-Miller J., The role and potential of sialic acid inhuman nutrition, Eur J Clin Nutr 2003;57:1351-1369, and Schnauer R.,Achievements and challenges of sialic acid research, Glycoconjugate J2000;17:485-499. Its role in cell communication covers regulation ofmolecular interactions, e.g. in the communication between cells andinfectious agents. It is a structural part of cell membrane molecules,such as gangliosides and glycoproteins.

The dietary aspects of the emerging knowledge on sialic acid function inthe human body have also been studied. Sialic acid is a major part ofhuman milk oligosaccharides, indicating a nutritional role. Furthermore,brain and saliva of breast fed infants were found to containsignificantly more sialic acid than those of infants fed commercialformula containing only minute amounts of sialic acid, suggesting aneffective absorption of this carbohydrate moiety (see Tram, T. H., etal., Sialic acid content of infant saliva: comparison of breast fed withformula fed infants, Arch Dis Childh 1997: 77-315-8, Wang, B., et al., Alongitudinal study of salivary sialic acid in preterm infants:Comparison of human milk-fed versus formula-fed infants, J Pediatr 2001;138:914-6 and Wang B., et al., Brain ganglioside and glycoprotein sialicacid in breastfed compared with formula-fed infants, Am J Clin Nutr2003;78:1 024-9).

Sialic acid exists in several chemical forms in nature. In body tissuesit is found as part of oligosaccharide chains bound to proteins orlipids with only little available as free sialic acid. In milk it ismainly bound to glycoproteins or free oligosaccharides. However, minorquantities are found as free or lipid bound sialic acid.

In human milk, the majority of sialic acid is bound to oligosaccharides.The concentration of oligosaccharides containing sialic acid varygreatly with lactation stage as well as individually. Several authorshave measured the content in human full term milk, finding contentsranging from more than 1 g/L in the first week to around 90-450 mg/L inmature milk (see Martin-Sosa, S., et al., Distribution of Sialic Acidsin the Milk of Spanish Mothers of Full Term Infants During Lactation, JPediatr Gastroenterol Nutr 2004;39:499-503, Carlson, S. E.,N-Acetylneuraminic acid concentrations in human milk oligosaccharidesand glycoproteins during lactation, Am J Clin Nutr 1985;41:720-6,Martin-Sosa, S., et al., Sialyloligosacchardies in Human and Bovine Milkand in Infant Formulas: Variations with the Progression of Lactation, JDairy Sci 2003;86:52-59, and Wang, B., et al. Concentration anddistribution of sialic acid in human milk and infant formulas, Am J ClinNutr 2001;74:510-5).

In contrast, the majority of sialic acid in bovine milk is bound toproteins. Bovine mature milk contains only little oligosaccharide boundsialic acid. In colostrums the content is around 230 mg/L, whereas it is25-54 mg/L in mature bovine milk (see Martin, M. J., et al.,Distribution of Bovine Milk Sialoglycoconjugates During Lactation, JDairy Sci 2001;84:995-1000, and Martin-Sosa, S., et al.,Sialyloligosacchardies in Human and Bovine Milk and in Infant Formulas:Variations with the Progression of Lactation, J Dairy Sci2003;86:52-59).

Bovine based infant and follow on formulas are produced from maturebovine milk and the content of oligosaccharide bound sialic acid inthese products has been found to be 15-35 mg/L, whereas that of pretermformulas was found to be slightly higher with 80 mg/L. Soy formulascontain no oligosaccharide bound sialic acid. See Wang, B., et al.Concentration and distribution of sialic acid in human milk and infantformulas, Am J Clin Nutr 2001;74:510-5 and Martin-Sosa, S., et al.,Sialyloligosacchardies in Human and Bovine Milk and in Infant Formulas:Variations with the Progression of Lactation, J Dairy Sci 2003;86:52-59.

With the sialyllactose concentrate of the present invention, infantformulas can be enriched with oligosaccharide bound sialic acid inconcentrations matching human milk, i.e. the total concentration ofoligosaccharide bound sialic acid can be increased to 100-1500 mg/Lmatching concentrations of human milk of various lactation stages.However, the scope of the present invention is not limited to this rangeof enrichment due to the great variations in human milk composition andalso due to the fact that other food applications may require otheroligosaccharide bound sialic acid concentrations.

Commercially, sialic acid containing ingredients for use in foods areavailable. One such ingredient is bovine sialic acid bound to theprotein κ-casein, commercially available from Arla Foods (Denmark) amongothers. Synthetically produced sources of sialic acid also exist, e.g.synthetic sialyllactose from MoBiTech, Germany, as well as recombinanthuman κ-casein containing sialic acid (see U.S. Pat. No. 6,270,827).

Thus, existing commercially available products containing sialic acidare either not obtained from natural sources, i.e. they are producedsynthetically or by using recombinant techniques, or they comprisesialic acid bound primarily to proteins and not oligosaccharides as inhuman milk. The product of the present invention is as far as we knowthe first product comprising a concentrate of oligosaccharidescontaining sialic acid which is derived from a natural ruminant milksource in a high concentration.

SUMMARY OF THE INVENTION

The present invention relates to a concentrate derived from a milkproduct enriched in naturally occurring sialyllactose in a milk product,so that the content of sialyllactose is from 0.32 to 25% by weight,based on dry matter. The concentrate can be dried. Such a sialyllactoseconcentrate powder obtained from a natural ruminant milk source areintended to be incorporated into various kinds of foods including, butnot limited to, infant formulas and other infant nutrition foods, childnutrition, functional foods and foods for medical and dietetic purposes.

Such a concentrate can according to the invention be prepared byultrafiltration of a milk product containing naturally occurringsialyllactose followed by diafiltration of the ultrafiltration retentateusing the same ultrafiltration membrane, optionally followed by reverseosmosis and/or drying, wherein the membrane is a thin film polyamidebased membrane.

DETAILED DESCRIPTION OF THE INVENTION

The concentrate of the invention has a content of sialyllactose from0.32 to 25% by weight, based on dry matter, preferably 0.4 to 25%, 1 to25%, 5 to 25%, 10to 15%.

The milk product can be milk or any milk product derived from a ruminantor another milk producing animal. The milk product can for example be abovine whey product, such as whey retentate or whey permeate. It canalso be the mother liquor from preparation of lactose from whey. It isalso possible to use, milk permeates, milk retentates, fractionated milkretentate or any other milk products containing sialyllactose.

The concentrate of the invention can be used as such, or it can befurther treated by for example reverse osmosis, crystallisation,affinity chromatography or a combination there of to remove water, or itcan be dried alone or together with one or more carriers. Any carrierscan be used, such as oil, fat, whey, demineralised whey, whey proteinconcentrate, whey protein isolate, other whey fractions, whey or milkpermeate or concentrate, skimmed milk, whole milk, semi-skimmed milk,milk fractions, maltodextrins, sucrose, lactose, native andpregelatinised starches, glucose syrups, casein and casein fractions.

The concentrate of the invention, including a dried concentrate can beused in any nutritional compositions, such as products for infantnutrition, protein bars, sports nutrition, drinks, health supplements,food for medical purposes and clinical nutrition. Infant nutrition canbe, but is not restricted to, infant formulas, follow-on formulas,infant cereal products or growing-up milk, i.e. modified milk or milkpowder suitable for children of 1-3 years.

The process will of course also work using two different thin filmpolyamide based membranes, manufactured by the same or differentmanufacturers, where one membrane is used for UF and the other for DIAfiltration. Alternatively combinations of two or more different thinfilm polyamide based membranes, manufactured by the same or differentmanufacturers, could be used simultaneously for UF and DIA filtration.It is necessary that the different membranes possess appropriate MWCOcut off values as described within this patent.

One preferred embodiment of the process of the invention uses a membranewith a suitable molecular weight cut off (MWCO) of 0.5-4 k Dalton with2.5 k Dalton being most preferable. 1, 1.5, 2, 3, 3.5 k Dalton are alsouseful.

The membrane is a thin film polyamide based membrane such as a GEOsmonics GH series membrane or a corresponding membrane normally usedfor ultrafiltration. The temperature is not critical, but normally 4-50°C. will be used, for example 5, 6, 7, 8, 9 or 10° C., but also highertemperatures such as 11, 12, 13, 14, 15 or even 20, 25, 30, 35, 40, 45or 50° C. can be used.

The pressure is not critical, but normally 1-40 bar will be used. Therecommendation of the membrane manufacturer can be used. The bestresults will normally be at 1-10 bar pressure, for example 2, 3, 4, 5,6, 7, 8, 9, or 10 bar, but also higher pressures such as 11, 12, 13, 14,15 or even 20, 25, 30, 35, or 40 bar can be used. The feed pressure canbe as low as 1 bar and as high as 50 bar. Typically feed pressures are5-6 bar or 10 bar. The best results are normally obtained using 1-10bar, but higher feed pressures will normally work, even if they are notas effective.

The present invention used cross-flow spiral wound membranes, howeverother membranes and configurations may alternatively be used.Alternative membranes and configurations may be, but are not limited tocross-flow filtration, dead-end filtration, plate and frame systems,cartridge systems, oscillating systems, flat sheet membranes, spiralwound membranes, fibre membranes, and tubular membranes. The membrane ishoused in a suitable process unit allowing contacting of the feed andmembrane with control of process parameters such as, but not limited to:temperature, pressure, flow rate, pH, etc. The membrane will separatethe feed into permeate and retentate process streams. Process streamsmay be completely removed from the process unit, or in some mannercompletely or partially recycled within the process unit and associatedsupply system (tanks and process streams). Prior to use, the membranesand process units are cleaned according to the membrane manufacturer'sinstructions, using manufacturer approved cleaning agents and processparameters.

Definitions and Special Equipment

In the present invention sialyllactose concentrations have been measuredusing high performance liquid chromatography (HPLC) equipped with a UVdetection system and a Shodex column, however and state of the arttechnique with acceptable accuracy may be employed.

Typical state of the art techniques include, but are not limited to:spectroscopic techniques, chromatographic techniques, enzyme assays,ELISA, other wet chemical assays, etc.

The present invention measured process stream lactose concentrationswith ATAGO® (Tokyo, Japan) model N1-E and N1-α refractometers and anenzymatic lactose assay kit from Roche (Boehringer Mannheim), howeverany state of the art technique with acceptable accuracy may be employed.There was a linear correlation (calibration curve) between processstream refractive index and the corresponding process stream lactoseconcentration as measured by the enzymatic lactose assay. Thecalibration curve allowed refractive index measurements to be used for“real time” estimation of lactose levels in the process streams.

Ultrafiltration (UF) is in the present invention defined as a membraneseparation process utilizing 0.5-500 k Dalton MWCO membranes, even if itwould be more correct to call a filtration utilizing a 0.5 k Daltonmembrane a nanofiltration process.

Diafiltration (DIA) is in the present invention defined as a membraneseparation process that adds water to the retentate, batch wise orcontinuous additions, and continues the removal of membrane permeatingspecies with the water.

Reverse osmosis (RO) is defined as essentially a dewatering techniquesremoving water and small aqueous solutes through the RO membrane.

An example of suitable ultrafiltration and diafiltration membranes areGE Osmonics (Minnetonka, Minn., USA) GH series membranes.

Typical industrial applications of GH membranes include: textile dyedesalting and concentration, colour removal from wastewater streams, andchemical purifications. GH membranes are typically not used in the dairyindustry, with this patent describing their first known usage forpurification of sialyllactose from a dairy derived feed.

Although the content of sialyllactose in ruminant milk is low relativeto the total carbohydrate content, surprisingly, an attempt toconcentrate sialyllactose was found to be successful. Through severalmembrane filtration techniques described below it was possible toproduce a nutritional compound with a content of sialyllactose of 1 w/w% to 40 wt/wt %, preferably 5 wt/wt % to 20 wt/wt %, a lactose contentof 1 wt/wt % to 95 wt/wt % and a protein content of 0 wt/wt % to 95wt/wt %.

The process may be run at any temperature as long as the manufacturersrecommended maximum temperature of 50° C. for GH series membranes is notexceeded.

Feed pH should not exceed the membrane manufacturers recommended maximumlimits, typically 1-13. The present invention uses dairy derivedmaterials as feed streams, which are typically, but not limited to, pH6-7. The dairy derived feed materials are fed directly to the processwithout the addition of acids, bases, buffers, or other materialscommonly used to standardize pH.

Differential membrane pressure should not exceed the membranemanufacturer's recommended maximum limits, typically 0.5-1.5 bar permembrane element. Feed pressure may be adjusted to give optimal membranepermeability, with higher pressures typically compressing the membranepores and affecting permeability. The present invention uses, but is notlimited to feed pressures of 1-40 bar. Feed pressures of 1-20 bar arepreferable with feed pressures of 5-10 bar being optimal for theOsmonics GH series membranes pH is not critical within the recommendedrange of 2 to 11.

The concentrate of the present invention containing highly elevatedlevels of sialyllactose can be produced by membrane filtration of a milkderived feed such as whey, milk, buttermilk, or fractions thereof. Themilk derived feed is ultrafiltrated to yield a sialyllactose richretentate with significantly reduced lactose and ash content. Thissialyllactose rich retentate is then diafiltered to further reducelactose and ash contents.

Optionally it is possible to further concentrate the concentrateobtained by ultrafiltration and diafiltration by reverse osmosis orother steps removing liquid without amendment of the content ofsialyllactose, based on the weight of dry matter. Thus theultrafiltration/diafiltration concentrate can be further concentratedvia reverse osmosis to a reverse osmosis concentrate with about 1-40%sialyllactose (wt/wt of dry matter). The process feed may besialyllactose ultrafiltration or diafiltration concentrates, a mixtureof sialyllactose ultrafiltration or diafiltration concentrates, amixture of fresh feed and sialyllactose ultrafiltration or diafiltrationconcentrates, or a diluted form of any of the aforementioned feeds. Theprocess runs until a desired level of sialyllactose concentration occursin the concentrate.

Crystallisation or affinity chromatography or both of these methods canalso be combined with the mentioned filtration techniques.

In another embodiment of the invention, the concentrate is dried aloneor with a suitable carrier material such as whey, demineralised whey,whey/WPI, other whey fractions, whey or milk permeate or concentrate,skimmed milk, whole milk, semi-skimmed milk, maltodextrins, sucrose,lactose, or native or pregelatinised starches, yielding an ingredientsuitable for incorporation in materials requiring sialyllactoseenrichment. The product can either be spray dried or freeze dried.

The sialyllactose concentrate is suitable for use in foods such as, butnot limited to, infant nutrition, protein bars, sports nutrition,drinks, health supplements, food for medical purposes and clinicalnutrition, supplying a daily physiologically interesting dose ofsialyllactose. However, it would also be technically and nutritionallyfeasible to incorporate it into other kinds of food applications.

The invention is further illustated by the following non limitingexamples.

EXAMPLE 1

3500 kg fractionated milk retentate was ultrafiltered using 12GH8040C1566 ultrafiltration membranes (GE Osmonics, material nr.1207118), a feed temperature of 10° C. and pressure of 5-7 bar.

After reduction of feed volume to 500 kg by ultrafiltration, batchdiafiltration (12×GH8040C1566 ultrafiltration membranes, GE Osmonics,material nr. 1207118) was applied at a feed temperature of 10° C. andpressure of 5-7 bar. Diafiltration water (3 additions, 1430 kg total)was added batch-wise to the filtration plant. The diafiltration ranuntil a diafiltration permeate refractive index≦0.1 brix.

Diafiltration yielded 106 kg diafiltration retentate, which wasconcentrated by reverse osmosis (1×SF3840 reverse osmosis membrane, GEOsmonics) at feed temperature of 5-10° C. and pressure of 25 bar.

Reverse osmosis filtration reduced the 106 kg diafiltration retentate to14.5 kg concentrate, which was dried to a final powder containing (wt/wtof dry matter): Sialyllactose 14% Lactose 44% Protein  8% Fat 0.1% Minerals  8%

This product will in the following examples be referred to as thesialyllactose concentrate.

EXAMPLE 2

1600 kg fractionated whey permeate was ultrafiltered using 18 GH3840-30Dultrafiltration membranes (GE Osmonics), a feed temperature of 10° C.and pressure of 5-7 bar.

After reduction of feed volume to 170 kg by ultrafiltration,diafiltration (18×GH3840-30D ultrafiltration membranes, GE Osmonics) wasapplied at a feed temperature of 10° C. and pressure of 5-7 bar.Diafiltration water (904 kg total) was added continuously to maintainconstant retentate volume in the filtration plant. The diafiltration ranuntil a diafiltration permeate refractive index≦0.2 brix.

Diafiltration yielded 170 kg diafiltration retentate: 0.4% dry weight,0.030% sialyllactose, and 0.22% lactose. This corresponds to asialyllactose concentrate containing 7.5% sialyllactose (wt./wt. of drymatter).

EXAMPLE 3

3000 kg fractionated whey retentate was ultrafiltered using 18GH3840-30D ultrafiltration membranes (GE Osmonics), a feed temperatureof 10° C. and pressure of 5-7 bar.

After reduction of feed volume to 170 kg by ultrafiltration,diafiltration (18×GH3840-30D ultrafiltration membranes, GE Osmonics) wasapplied at a feed temperature of 10° C. and pressure of 5-7 bar.Diafiltration water (1241 kg total) was added continuously to maintainconstant retentate volume in the filtration plant. The diafiltration ranuntil a diafiltration permeate refractive index≦0.5 brix.

Diafiltration yielded 170 kg diafiltration retentate, which wasconcentrated to 21.29 kg by reverse osmosis (1×SF3840 reverse osmosismembrane, GE Osmonics) at feed temperature of 5-10° C. and pressure of25 bar.

8.63 L reverse osmosis concentrate was batch diafiltered (1×GH3840-30Ddiafiltration membrane, GE Osmonics) at a feed temperature of 10° C. andpressure of 5-7 bar. Diafiltration water (3 additions, 69.5 kg total)was added batch-wise to the filtration plant. The diafiltrationretentate was dried to a sialyllactose concentrate containing 7.17%sialyllactose (wt/wt of dry matter).

EXAMPLE 4

The sialyllactose concentrate produced in Example 1 is mixed in a mixingvat with a whey protein concentrate containing 80 wt/wt % protein(Lacprodan 80, Arla Foods, Denmark) until completely dissolved. The wheyprotein concentrate is added through a powder addition funnel connectedto the flow of the recirculation of the sialyllactose concentrate.Sialyllactose concentrate and the whey protein concentrate is mixed in acombination of 33% sialyllactose concentrate and 66% whey proteinconcentrate.

The mixed concentrate is led through an in-line mixer before returningto the mixing vat, where it is agitated. After mixing, the concentrateis pumped to a new vat, from which it is pumped through a platepreheater (preheating temperature of 75° C.) to the spray tower. Bymeans of a high pressure pump the mix is pumped to a Niro spraytower andsprayed with the following conditions: Spray pressure 195 bar NozzlesDelawan 4 × 28/54 Hot air temp 200° C. Exhaust air temp 92° C.

These processes yielded a final sialyllactose concentrate protein powderwith the following composition (wt/wt of dry matter): Sialyllactose 5%Lactose 21%  Protein 60%  Fat 6% Minerals 8%

EXAMPLE 5

In this example of the present invention, a milk based starter infantformula is enriched with the sialyllactose concentrate, but otherformulas such as follow on, growing up, preterm or soy based formulascould also be enriched in a similar way and are therefore consideredcovered by this example. The examples are prepared to fulfill the EUlegalisation (Commision Directive 91/321/EEC on infant formulae andfollow-on formulae) regarding concentrations of fat, protein,carbohydrates and ashes.

In the calculations of this example of the present invention, it isassumed that the natural concentration of oligosaceheride bound sialicacid in bovine milk based infant formula is 30 mg/L. The targetconcentration after enrichment is 260 mg/L, which is within the range ofthe content of mature human milk.

In table 1, the nutrient distribution of typical ingredients used for astarter infant formula as well as of the final formula is shown. In theexample of table 2, the same infant formula is enriched with 2.369 gsialyllactose concentrate per 100 g powder, which equals 354 mgsialyllactose or 173 mg oligosaccharide bound sialic acid per 100 gpowder. With a powder addition of 133 g per L, the formula is enrichedwith 230 mg oligosaccharide bound sialic acid per L. On top of this, anatural oligosaccharide bound sialic acid content of around 30 mg/L isalso present in the formula, making the total oligosaccharide boundsialic acid content about 260 mg/L.

The infant formula of the example presented in table 3 is enriched with7.080 g sialyllactose concentrate protein powder per 100 g formula,which equals 354 mg sialyllactose or 173 mg oligosaccharide bound sialicacid per 100 g powder. As above, the powder addition was 133 g per L,resulting in an enrichment with 230 mg oligosaccharide bound sialic acidper L on top of the natural oligosaccharide bound sialic acid content ofaround 30 mg/L, totalling a oligosaccharide bound sialic acid content ofabout 260 mg/L of the final formula. TABLE 1 Nutrient distribution ofthe ingredients of a typical starter infant formula as well as that ofthe final formula with a casein to whey protein ratio of 40/60 AdditionFat Protein Carbohydrates Ash Ingredient g/100 g powder Fats and 25.25525.255 0 0 0 oils solids Skimmed milk 17.271 0.177 6.601 8.978 1.402solids Whey protein 8.100 0.567 6.399 0.891 0.234 concentrate solidsLactose 44.514 0 0 44.514 0 Minerals 1.360 0 0 0 1.360 Vitamin 0.500 0 00.460 0 preblend Moisture 3.000 0 0 0 0 Nutrient 26.00 13.00 54.77 3.00distribution in infant formula

TABLE 2 Nutrient distribution of the ingredients of a starter infantformula as well as that of the Final formula with a casein to wheyprotein ratio of 40/60 and enriched with the sialyllactose concentrateof Example 1 of the present invention Addition Fat Protein CarbohydratesAsh Ingredient g/100 g powder Fats and oils 25.227 25.227 0 0 0 solidsSkimmed milk 17.271 0.177 6.601 8.978 1.402 solids Whey protein 7.5000.525 5.925 0.825 0.225 concentrate solids Lactose 43.133 0 0 43.106 0Sialyllactose 2.369 0.071 0.472 1.44 0.377 concentrate Minerals 1.000 00 0 1.000 Vitamin 0.500 0 0 0.460 0 preblend Moisture 3.000 0 0 0 0Nutrient 26.00 13.00 54.81 3.00 distribution in infant formula

TABLE 3 Nutrient distribution of the ingredients of a starter infantformula as well as that of the final formula with a casein to wheyprotein ratio of 40/60 and enriched with the sialyllactose concentrateprotein powder of Example 2 of the present invention Addition FatProtein Carbohydrates Ash Ingredient g/100 g powder Fats and oils 25.20825.208 0 0 0 solids Skimmed milk 17.271 0.177 6.601 8.978 1.402 solidsWhey protein 2.717 0.190 2.146 0.299 0.082 concentrate solids Lactose43.274 0 0 43.231 0 Sialyllactose 7.080 0.425 4.248 1.841 0.566concentrate protein powder Minerals 0.950 0 0 0 0.950 Vitamin 0.500 0 00.460 0 preblend Moisture 3.000 0 0 0 0 Nutrient 26.00 13.00 54.81 3.00distribution in infant formula

For simplicity the different minerals and vitamins are not specified,but it is clear that the mineral and vitamin additions should beadjusted according to the contribution from the sialyllactoseconcentrate and the sialyllactose concentrate protein powder. Also, forcalculation of the 40/60 casein/whey protein ratio, the protein of thesialyllactose concentrate and the sialyllactose concentrate proteinpowder are considered as whey protein, and furthermore, thesialyllactose of these two ingredients are considered as carbohydrate.Part of the nitrogen of the sialyllactose concentrate and thesialyllactose concentrate protein powder is not true protein meaningthat the protein level should be adjusted accordingly, but forsimplicity reasons this is not included in the example.

1. A concentrate derived from a milk product enriched in the naturallyoccurring sialyllactose in the milk product, so that the content ofsialyllactose is from 0.32 to 25% by weight, based on dry matter.
 2. Aconcentrate according to claim 1 wherein the content of sialyllactose isfrom 0.4 to 25% by weight, based on dry matter.
 3. A concentrateaccording to claim 1 wherein the content of sialyllactose is from 1 to25% by weight, based on dry matter.
 4. A concentrate according to claim1 wherein the content of sialyllactose is from 5 to 20% by weight, basedon dry matter.
 5. A concentrate according to claim 1 wherein the contentof sialyllactose is from 10 to 15% of the weight, based on dry matter.6. A concentrate according to claim 1, wherein the milk product is awhey product.
 7. A concentrate according to claim 1, wherein the milkproduct is a whey retentate.
 8. A concentrate according to claim 1,wherein the milk product is a whey permeate.
 9. A composition containinga concentrate according to claim 1, which is dried alone or togetherwith one or more carriers.
 10. A composition containing a concentrateaccording to claim 1, which is dried together with one or more carrierschosen from the group consisting of oils and fats, whey, demineralisedwhey, whey protein concentrate, whey protein isolate, other wheyfractions, whey or milk permeate or concentrate, skimmed milk, wholemilk, semi-skimmed milk, milk fractions, maltodextrins, sucrose,lactose, native and pregelatinised starches, glucose syrups, casein andcasein fractions.
 11. A nutritional composition chosen from the groupcomprising infant nutrition, protein bars, sports nutrition, drinks,health supplements, food for medical purposes and clinical nutrition,containing a concentrate according to claim 1 or a composition accordingto claim
 9. 12. A composition according to claim 11 chosen from thegroup consisting of an infant formula, follow-on formula, infant cerealproduct or growing-up milk.
 13. A process for the preparation of aconcentrate according to claim 1 comprising ultrafiltration of a milkproduct containing naturally occurring sialyllactose followed bydiafiltration of the ultrafiltration retentate using the sameultrafiltration membrane, optionally followed by reverse osmosis andor/drying, wherein the membrane is a thin film polyamide based membrane.14. A process of claim 13, wherein the molecular weight cut off (MWCO)value is 0.5-4 k Dalton.
 15. A Process of claim 14, wherein themolecular weight cut off (MWCO) value is 2.5 kD.
 16. A process accordingto claim 13, wherein the ultrafiltration and diafiltration is run at atemperature between 2° C. and 50° C. and a feed pressure between 1 and50 bar.
 17. A process according to claim 13, wherein the ultrafiltrationand diafiltration is run at a temperature between 4° C. and 15° C. and afeed pressure between 5 and 20 bar.
 18. A process according to claim 13,wherein the ultrafiltration and diafiltration is run at a temperature ofabout 10° C. and a feed pressure of about 5-7 bar.
 19. A processaccording to claim 13, wherein the composition is further treated byreverse osmosis, crystallisation, chromatography, drying or acombination thereof or drying together with one or more carriers.
 20. Aprocess of claim 13, wherein the milk product is a whey product.
 21. Aprocess of claim 13, wherein the milk product is a product chosen fromthe group consisting of whey permeate, whey retentate, fractionated milkretentate or milk permeate.
 22. A process of claim 13, wherein the milkproduct is mother liquid from lactose production.
 23. A concentrateobtainable by the process of claim 13.